This invention relates to apparatus for generating an electrical signal indicative of the level of a liquid stored in a reservoir.
Although many devices have been developed for indicating liquid level, accurate and reliable, but inexpensive, devices for providing a remote indication of potatable or waste water level are not generally available. A device for this purpose should not be subject to malfunction resulting from contaminated and impure water. Also, it should be insensitive to electrical noise, should have a substantially linear indication of liquid level, should permit remote indication thereof and should be easily installed in the liquid reservoir. For use in conjunction with a mobile reservoir, for example, to provide a liquid level indication for the water or waste stored in a tank of a recreational vehicle, the electrical liquid level indicating apparatus should be able to operate using a conventional Dc voltage supply, such as a vehicle twelve-volt storage battery.
Electrical liquid level indicating devices of the prior art have generally been unsuitable for the indication of potable or waste water level due to their sensitivity to impurities in the water or because the conductivity of the water varies too greatly or renders use of the electrical liquid-level indicating apparatus impractical. Also, electrical liquid-level indicating apparatus which requires direct electrical contact of metal probes or the like with water may prove unsatisfactory due to the electolytic effect of the water on the metal probe. This electrolytic effect corrodes metal parts and, with respect to potable water, contamination may result.